Methods using indicators such as bicaudate index (Bicaudate Cerebroventricular Index (CVI)) exist for the determination of brain atrophy. The portions flanked by the caudate nuclei is referred to as the anterior horns of the lateral ventricles, and these methods assess atrophy based on the value of the ratio between the width of the portion where a line passing through the caudate heads (heads of the caudate nuclei) intersects the lateral ventricles and the width of the portion where a line passing through the caudate heads intersects the outer sides of the frontal lobe (width of the frontal lobe). When this ratio exceeds a given value (for instance 15%), the brain is determined to be in an atrophic state. There are other methods taking the ratio of other locations to assess cerebral atrophy.
FIG. 6 is a figure showing an example of prior art cerebral atrophy assessment method. FIG. 6 (a) shows the locations of measurements by the bifrontal index, and FIG. 6 (b) shows the locations of measurements by the bicaudate index.
In addition, for imaging of brain tissues, it has been shown that extraction could be carried out from nuclear magnetic resonance (MRI) images according to the characteristics of each tissue such as white matter and grey matter to carry out computation of the surface area of each tissue in the slice plane (refer to Patent References 1 and 2 and Non-patent References 1 to 3).    Patent Document 1: Japanese Unexamined Patent Application Publication No. 2004-174218    Patent Document 1: Japanese Unexamined Patent Application Publication No. 2004-174220    Non-Patent Document 1: The Institute of Electronics, Information and Communication Engineers, D-II Vol. J87-D-II no. 1 pp. 117 to 125, 2004    Non-Patent Document 2: IEEE Trans. On Medical Imaging, Vol. 22 No. 1 pp. 105 to 119, 2003    Non-Patent Document 3: Computer Aided Diagnosis Theses, Vol. 2 No. 2 99. 1 to 7, 1998 Image